An implication of novel methodology to study pancreatic acinar mitochondria under in situ conditions

Mitochondria maintain numerous energy-consuming processes in pancreatic acinar cells, yet characteristics of pancreatic mitochondrial oxidative phosphorylation in native conditions are poorly studied. Besides, it is not known which type of solution is most adequate to preserve functions of pancreatic mitochondria in situ. Here we propose a novel experimental protocol suitable for in situ analysis of pancreatic mitochondria metabolic states. Isolated rat pancreatic acini were permeabilized with low doses of digitonin. Different metabolic states of mitochondria were examined in KCl- and sucrose-based solutions using Clark oxygen electrode. Respiration of digitonin-treated, unlike of intact, acini was substantially intensified by succinate or mixture of pyruvate plus malate. Substrate-stimulated respiration rate did not depend on solution composition. In sucrose-based solution, oligomycin inhibited State 3 respiration at succinate oxidation by 65.4% and at pyruvate plus malate oxidation by 60.2%, whereas in KCl-based solution, by 32.0% and 36.1%, respectively. Apparent respiratory control indices were considerably higher in sucrose-based solution. Rotenone or thenoyltrifluoroacetone severely inhibited respiration, stimulated by pyruvate plus malate or succinate, respectively. This revealed low levels of non-mitochondrial oxygen consumption of permeabilized acinar cells. These results suggest a stronger coupling between respiration and oxidative phosphorylation in sucrose-based solution.